(1) Field of the Invention
This invention relates to a safety device for a medical needle, to confer passive protection for a needle with which the device is associated. The invention also relates to a safety needle assembly
The safety device of this invention has been designed for use with a medical needle having a sharp tip, intended for penetration of a human or animal body, or for other medical uses such as the penetration of a pierceable membrane or of an intravenous medication system. For convenience reference will be made herein solely to the penetration of a body, even though specific embodiments of this invention may be intended for other medical uses.
Throughout this specification, reference is made to the relative terms “forward” and “rearward”; “forward” and “forwardly” refer to the end of the device which is presented to a body when a medical procedure is to be performed (that is, the tip end of the needle) and the direction towards that end; and the terms “rearward” and “rearwardly” refer to the other end of the device (that is, the end of the device nearer a syringe with which the device may be used) and the direction towards that other end.
(2) Description of the Related Art
Fluids of various kinds may be administered to a human or animal body by means of a hollow needle in conjunction with a source of the required fluid. For example, such a needle may be used in conjunction with a syringe holding a liquid drug which may be contained directly in the syringe barrel or in a cartridge located within the syringe, the needle being used to penetrate the body at the site at which the drug is to be received. Equally, body fluids may be withdrawn by using a hollow needle which is used to penetrate the body until the tip is located at the site from which fluid is to be withdrawn.
A recognized hazard for clinicians and other persons using medical needles for the above described purposes, as well as people who may be exposed to used needles in the course of the disposal of those needles, is the risk of a so-called needle-stick injury—that is to say the accidental penetration of a person's skin by the needle. Prior to the use of the needle to supply a fluid to or to withdraw fluid from a body, this rarely presents much of a problem, though once the needle has been used on a body, there is a very much higher risk of a serious consequence for a person suffering a needle-stick injury. During use of the needle to penetrate the body tissues of a patient, the needle is likely to become contaminated with various organisms; should a person subsequently suffer a needle-stick injury, infection could occur.
There have been numerous proposals for protecting the sharp tip of a used needle, in order to reduce the risk of a needle-stick injury following use of the needle. Some proposals have actually increased the likelihood of such an injury by virtue of the action which must be performed to protect the tip, even if the risk thereafter is lessened. Despite all of the proposals which have previously been made, very few have achieved commercial success, nor has there been wide acceptance by the medical industry. Many proposals are somewhat complex and involve a significantly greater manufacturing cost, and so are unacceptable on economic grounds. Others are much more difficult to use as compared to an unprotected needle, and so are rejected by clinicians. Yet further proposals do not allow compliance with best practice protocols.
A device which protects a needle tip after use without an operator having to perform any extra step on withdrawing the needle from a body is usually referred to as a passive protection device. This may be contrasted with an active protection device, where an operator is required to perform an extra step in order to protect a needle, following the withdrawal of the needle from a body. The requirement to perform an extra step leaves the needle unprotected for a longer period than with a passive protection device and further the performance of that extra step exposes the operator to a potentially hazardous situation, when needle-stick accidents can occur
There is a significant demand for a passive protection device for use with a needle, and which allows a clinician or perhaps others to use the needle in much the same way as is done with an unprotected needle, but which can be manufactured economically and which provides a high degree of protection against needle-stick injury. In the case of health professionals, this demand is driven by health and safety legislation but in the case of others performing self-injections using a so-called pen injector, the used needles must be disposed of safely with minimum risk to others, even in the event that a sharps container is not immediately available. Further, particularly for self-injections, it is highly preferred that the device operates fully automatically without intervention by the user, so as wholly to prevent access to the needle tip after use other than by a determined attempt to override the protection. In this way, protection may be afforded not just to the clinician or other user of the needle, but also to people who could come into a risky situation with used needles, such as waste disposal operators, cleaners, and so on.
It is often advantageous for a safe needle device having a sleeve to shroud a needle to have an intermediate setting where the needle tip is exposed to a small extent, before use. This is to allow purging of air from the syringe and needle, and also to allow the operator to observe the precise point of penetration of a body. When full protection is to be achieved after performing an injection, the sleeve is moved to a position where the needle is wholly covered, and so to a position further forwardly with respect to the needle than the intermediate setting. If a spring is arranged to provide a force on the sleeve to move it to the final fully-protecting position, that spring will be pre-loaded, when the sleeve is in the intermediate setting.
The pre-loading of a spring is not normally an issue if the spring is of metal. However, to reduce manufacturing costs, it is possible to provide a plastics material spring and in that case, the safe needle device must be stored in such a setting that the spring is not pre-loaded, having regard to the memory effect associated with plastics, especially when stored for long periods. One solution to this problem is by moving the sleeve to the intermediate setting immediately before the safe needle device is to be used to perform an injection. An alternative would be to ensure the spring is not pre-loaded even at the intermediate setting, but arranging the device so that the spring is subsequently loaded during the performance of an injection to provide a sufficient force on the sleeve which will move the sleeve to its protecting position.
The present invention aims at providing a safety needle device for a syringe or other injector which addresses these issues and which is both relatively simple and economic to manufacture, especially on a fully automated production line, and which does not significantly affect a conventional injection procedure when mounted on an injector, including the steps of purging the syringe and needle of air, and observing the needle tip as the needle is inserted in the required injection site.